Progressive-burning smokeless powder and method of manufacture



Patented Jan.- 23, 1940 PROGRESSIVE-BURNING SMOKELESS POW- DER AND METHOD OF MANUFACTURE Harold M. Spurlin and Gustave H. Pfeifier, Wilmington, Del., assignors tov Hercules Powder Company, Wilmington, Del,

Delaware a corporation of No Drawing. Application December 28, 1936, Serial No. 117,890

12 Claims.

This'invention relates to an improved method of preparation of progressive-burning smokeless powder and more particularly to an improved method of coating smokeless powder with a deterrent material, and to smokeless powder coated with a deterrent material.

As is well known, in order to render possible close control of the burning rate of smokeless powder and produce a high velocity of the pro- :lectile without high breech pressures, it has been customary to coat the grains of the smokeless powder with a deterrent material, explosive or non-explosive, which will retard the initial burning rate of the powder grains. Such coating material penetrates the powder grains more or less, so that as the powder burns, the successively exposed surfaces contain gradually less and less of the deterrent material, thus causing the combustion of the grains to proceed with increasing speed.

In order to effect thecoating of smoke less powder grains with a deterrent material, numerous processes have been devised, e. g., using dinitrotoluene as the deterrent material, powder grains coated with dinitrotoluene are subjected to heat, with or without the presence of moisture or water. By another method, the powder grains are coated by treatment with a solution of dinitrotoluene in benzene, the benzene evaporated, and penetration of the dinitrotoluene into the grain of powder obtained by immersing the coated powder grains in a hot water bath for several hours or several days. By still another method, using as the deterrent material a mixture of dimethyldiphenyl urea and dinitrotoluene, or dimethyldi'phenyl urea alone, the powder grains and deterrent material are covered with water, and after mixing, heat is applied for varying periods.

By still another method the powder grains are surface treated by an alkyl phthalate, either in solution or in aqueous emulsion.

By the use of deterrents'which are solvents for the nitrocellulose of the powder grain, great difilculty is experienced in the sticking together or the clustering of the powder grains. This is completely avoided by the use of my invention described below.

Treatment of smokeless powder grains to render their combustion progressive by applying thereto a deterrent by methods heretofore known, while producing the desired results to a degree, has been open to a number of objections. The deterrents heretofore used have been more or less good solvents for the nitrocellulose of the smokeless powder, and consequently, even if apdue to the disappearance plied on the surface of the powder grain, have penetrated to a depth into the powder grain depending upon the conditions of treatment, e. g., a longer time of heating of the powder grains with the deterrent or solution of the deterrent causing a deeper penetration of the deterrent into the powder grains than would otherwise be the case. 7

Powder grains treated with a deterrent which is a solvent for the nitrocellulose of the powder grains tend to penetrate more and more deeply into the powder grains during storage of such progressive-burning smokeless powder, particu-v larly during storage of said powder during hot periods of the year or in hot climates, and consequently the concentration of the deterrent on the surface of the powder grain becomes less and less with the age of the powder grain, and the deterrent action on the surface of the powder grain consequently becomes less and less on stor- 20 age. The result thereof is that powder grains deterred by a deterrent which is a solvent of the nitrocellulose in the powder grain, do not remain ballistically stable, 1. e., the ballistics of the powder change with of the deterrent from the surface of the powder grains.

Now in accordance with our invention we may utilize as a deterrent for smokeless powder grains,

the age of the powder as a non-volatile, non-explosive organic substance with the nitrocellulose of the powder grains, but which is a non-solvent therefor. As a consequence of being compatible with the nitrocellulose, without being a solvent which is compatible therefor, the deterrents which we may use adhere strongly to the surface of the powder grain without rendering the grains sticky or penetrating deeper into thegrain on storage, and thus altering the characteristics of the powder on storage. We have been unable to determine deflnitely whether or not the deterrents which we may use penetrate into the surface of the powder grains at all. We believe that they penetrate mechanically to a slight extent. If, however,

such penetration takes place, it either does not 45 continue on storage, or if it does, it progresses so slowly as to have practically no eflfect on the ballistics of the powder.

We may apply our improved deterrents to the smokeless powder grain in solution in a solvent 50 for the deterrent which is not a solvent for the smokeless powder, in an aqueous emulsion or otherwise as may be desirable and convenient.

As examples of deterrents which we may uti-' lize to coatthe grains of smokeless powder in accordance with this invention, we may use the alkyl esters of the fatty acids, as, alkyl esters of ricinoleic acid, alkyl esters of polymerized ricinoleic acid, etc.; rosin esters, as, monohydric alcohol esters of abietic acid, polyhydric alcohol esters of abietic acid, monohydric alcohol esters of pimaric acid, polyhydric alcohol esters of pimaric acid, etc.; synthetic lacquer resins, as, the modifier or unmodified polyhydric alcohol-polybasic acid resins (alkyds, rezyls, etc.), phenol-formaldehyde type resins, etc.; rosins, as, wood rosin, gum rosin, etc.; hydrogenated rosins, as hydrogenated wood rosin, hydrogenated gum rosin, etc.; and the like. Thus, We may use butyl ricinoleate, butyl acetyl ricinoleate, butyl ester of polymerized ricinoleic acid, methyl abietate, ethyl abietate, hydrogenated methyl abietate, hydrogenated ethyl abietate, ester gum, hydrogenated ester gum, modified or unmodified glycerolphthalate resin, oil-modified phenol-formaldehyde type resins, glycerol sebacate, glycol sebacate, glycerol-glycol sebacate, modified or unmodified ethylene glycol terpinene maleic anhydride resins, modified or unmodified diethylene glycol terpinene maleic anhydride resins, modified or unmodified triethylene glycol terpinene maleic anhydride resins, modified or unmodified glycerol terpinene maleic anhydride resins, etc.

As an example of the carrying out of the process involving our invention and producing our improved product, 908 parts by weight of a double base smokeless shotgun powder, containing nitroglycerin, were placed in a cold sweetie barrel, and to this was added slowly 27 parts by weight of butylacetyl ricinoleate dissolved in about 160 parts by weight of cold ethyl alcohol, the mixture tumbled in a closed sweetie barrel at room temperature for about hour, after which the powder was removed to a dry house and dried for one day at 55 C., then graphited,-screened and exposed to an atmosphere of -60% relative humidity to bring the moisture content to equilibrium.

In a further example of carrying out our process and the making of the product according to our invention, 908 parts by weight of a double base shotgun powder containing 20% nitroglycerin was treated in a manner identical with the above example with 27 parts by weight of" hydrogenated methyl abietate.

In a further example of our process and product, 908 parts by weight of a 10% nitroglycerin shotgun powder were coated with 5% of hydrogenated methyl abietate in the manner described above.

In the coating operation We may use only sufficient volatile solvent containing the deterrent to wet the powder grains, or we may use a large excess of solvent which can be removed by evaporation or otherwise. We may treat smokeless powder with the deterrent at temperatures ranging between 0 and 100 C., and we may treat the smokeless powder grains with our improved deterrent, alone or in solution, for varying lengths of time, depending upon the composition of the powder treated, and the size of the powder grains. As solvent for the deterrent, we may use any convenient solvent which has no appreciable solvent action upon the nitrocellulose of the powder grains, for example, ethyl alcohol, propyl alcohol, isopropyl alcohol, petroleum hydrocarbons, as benzene, petroleum ether, and ether such as, diethyl ether; and we may coat either single base powder grains or double base powder grains.

As an example of the heat stability of smokeless powder prepared in accordance with this invention as compared with smokeless powder prepared in accordance with the old art, using as deterrent a solvent of nitrocellulose, the following table is given:

Powder Velocity Pres Condition of Y (21:11-53 Deterrent used foot/Sea I charge 38.5.. Di-ethyl phthalatc.. 1, 015 11,000 Fresh. 38.5 do 1,022 14,500 Stored 10 days at C. 30.5". Butyl ester of poly- 979 10. 300 Fresh.

merized ricinoleic acid. 36.5 ..do 978 11, 100 Stored 10 days at 55 C. 36.5 Butylacetyl ricino- 989 11, 100 Fresh.

leate. 36.5 c ..do 989 11,400 Stored 10 days 1 at 55 C. 37.0 Butyl ricinoleate 989 12,100 Fresh. 37.0 "do 980 11, 700 Stored 10 days at 55 C. 36.5 Hydrogenatedmeth- 1,011 11,100 Fresh.

yl abietate, 36.5 .do l c 1,016 11, 200 Stored 29 (lays v at 50 C.

It will be noted that with the old art powders (coated with diethyl phthalate), there was an increase in pressure after hot storage of 3,500

lbs. per sq. in., whereas with the smokeless powder prepared in accordance with the present invention, there is either a decrease in pressures for the same charge and the same velocity, or at most an increase in pressure of only 300 lbs. per sq. in.

It will be understood that where we have referred to a compound as being a non-solvent for nitrocellulose, we mean a compound which, by reason of its relatively low content of chemical groups which are known to promote solvent action, its high molecular weight, its high viscosity at temperatures to which the compound may be subjected, or its structural arrangement, does not dissolve nitrocellulose of the degree of nitration used in a particular case, at a measurable rate of solution.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as herein broadly described and claimed is in no way limited -thereby.

What we desire to claim and ters Patent is:

1. Inthe method for the preparation of progressive burning smokeless powder the step which comprises surface coating smokeless powder grains with an alkyl ester of a higher fatty acid which is a non-volatile, non-explosive deterrent and which is a non-solvent for nitrocellulose but compatible therewith.

2. In the method for the preparation of progressive burning smokeless powder the step which comprises surface coating smokeless powder grains with an alkyl ester of ricinoleic acid which is a non-volatile, non-explosive deterrent and which is a non-solvent for nitrocellulose but compatible therewith.

3. In the method for the preparation of progressive burning smokeless powder the step which comprises surface coating smokeless powder grains with butylacetyl ricinoleate.

4. As a new product, smokeless powder grains surface coated with an alkyl ester of a higher fatty acid which is a non-volatile, non-explosive deterrent and which is a non-solvent for nitro-. cellulose but compatible therewith. r

5. As a new product, smokeless powder grains protect by Letsurface coated with an alkyl ester of ricinoleic acid which is a non-volatile, non-explosive deterrent and which is a non-solvent for nitrocellulose but compatible therewith.

6. As a new product, smokeless powder grains surface coated with butylacetyl ricinoleate. 7. In the method of preparing a progressive burning smokeless powder characterized by nearly complete freedom from progressive penetration of the powder grains by the deterrent coating when the powder is aged under normal storage conditions, the step which comprises surface-coating smokeless powder grains without substantial initial deterrent penetration beneath the surface of the grains, the said penetration being largely mechanical but slight in any event, with a non-volatile, non-explosive organic deterrent which is a non-solvent for nitrocellulose but compatible therewith.

8. As a new product, smokeless powder grains characterized by nearly complete freedom from progressive penetration of the powder grains by the deterrent coating when the powder is aged under normal storage conditions, surface-coated without substantial initial deterrent penetration beneath the surface of the grains, the said penetration being largely mechanical but slight in any event, with a non-volatile, non-explosive organic deterrent which is a non-solvent for nitrocellulose but compatible therewith.

9. In the method for the preparation of progressive burning smokeless powder, the step which comprises surface-coating smokeless powder grains with butyl ricinoleate.

10. In the method-for the preparation of progressive burning smokeless powder, the step which comprises surface-coating smokeless powder grains with the butyl ester of polymerized ricinoleic acid.

11. As a new product, smokeless powder grains surface-coated with butyl ricinoleate.

12. As a new product, smokeless powder grains surface-coated with the butyl ester of polymerized ricinoleic acid.

HAROLD M. SPURLIN. GUSTAVE H. PFEIFFER. 

